Ethylene glycol is an important chemical raw material and strategic material in China. Ethylene glycol can be used to produce polyester which can be further processed to produce terelyene, PET bottles and thin films, explosives, glyoxal. Ethylene glycol can also be used as antifreeze, plasticizers, hydraulic fluids, solvents and so on. In 2009, the Chinese import quantum of ethylene glycol was more than 5.80 million tons. It is expected that in 2015, Chinese ethylene glycol demand will reach 11.20 million tons, and Chinese production capacity of ethylene glycol will be about 5 million tons, and the supply and demand gap will be 6.20 million tons. Therefore, there is a good market prospect for development and application of new production technology of ethylene glycol in china. Internationally, ethylene oxide is mainly obtained by oxidation of ethylene generated from petroleum cracking, and ethylene glycol is mainly obtained by hydration of ethylene oxide. In view of the current state of Chinese energy source structure of being rich in coal, lack in oil and gas, and the crude oil price being kept at a high level for a long time, the process of producing ethylene glycol from coal as a new technique in coal chemistry industry is the most practical choice of the coal chemistry industry in the future, because it can ensure the national energy safety and make full use of the coal resource in China.
At present, the relatively mature technology in China is a complete set of technology containing CO gas phase catalytic synthesis oxalate ester and catalytic hydrogenation synthesis of ethylene glycol from oxalate ester, developed by Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences.
In early December 2009, the coal-to-ethylene glycol project of GEM Chemical Company, Tongliao, Neimenggu with a yearly output of 200 thousand tons, has been successful in getting through the entire process in the first-stage project and produced a qualified ethylene glycol product, which is the world first industrial demonstration device, attracting industry attention.
However, due to relatively more industrial units, high requirement of industrial gases purity, usage of noble metal catalysts in the process of oxidative coupling, and utilization of nitrogen compounds with potential environment pollution, the technology process has been restricted in economic efficiency, environmental protection, energy-saving performance and further industrial scale-up.
Polyoxymethylene dimethyl ethers (or polymethoxy acetal) with molecular formula of CH3O (CH2O) nCH3 with n≥2, generally is abbreviated as DMMn (or PODEn). In the process of preparing polyoxymethylene dimethyl ethers, the product distribution is not very appropriate with a high selectivity of methylal and DMM2 and a low selectivity of DMM3-4 which can be used as the additives of diesel. To obtain DMM3-4, it is necessary to contain the repeated separation and reaction steps of the side products which are produced in the preparing process, bring a high energy consumption and a low economic efficiency. Therefore, if the side products methylal and DMM2 can be directly produced into more economically valuable products, it will improve the economic efficiency of the process.
In US2010/0105947A, a method for preparing methyl methoxyacetate has been disclosed, in which methyl methoxyacetate was prepared by dimethoxymethane carbonylation, in the presence of a zeolite molecular sieve catalyst. The catalyst has been selected from FAU, ZSM-5, MOR or β-zeolite. In EP0088529A2, a method for preparing methyl methoxy acetate has been disclosed, in which methyl methoxy acetate was obtained by dimethoxymethane carbonylation, in the presence of a solid catalyst. The catalyst is selected from acidic cation exchange resins, clays, zeolites, solid acids, inorganic oxides, inorganic salts and oxides. In CN104119228A, a method for preparing methyl methoxy acetate has been disclosed, in which methylal and CO were used as raw materials to prepare methyl methoxy acetate by catalytic synthesis, and the catalyst is a molecular sieve with MWW framework structure. In CN103894228A, a method for preparing methyl methoxy acetate has been disclosed, in which methylal and CO were used as raw materials to prepare methyl methoxy acetate by catalytic synthesis, and the catalyst is a solid catalyst loaded with a strong organic sulfonic acid. The supporter of the catalyst is one or more selected from activated carbon, SBA-15 and MCM-41. In CN103172517A, a method for producing methyl methoxy acetate has been disclosed, in which the methyl methoxy acetate was produced by gas-phase carbonylation of methylal and CO, in the presence of a solid acid catalyst. In recent years, Professor Alexis T. Bell from University of California Berkeley has proposed a new route to producing ethylene glycol, containing gas-phase carbonylation of methylal for preparing methoxy acetic acid methyl ester and hydrogenated hydrolysis of methoxy acetic acid methyl ester to producing ethylene glycol. And the most important step is the gas-phase carbonylation. However, because the catalyst life is short, and the concentration of methylal in raw gas is low, and the conversion rate of methylal and the selectivity of methyl methoxy acetate are not ideal, it is far from industrialization. (Angew. Chem. Int. Ed., 2009, 48, 4813-4815; J. Catal., 2010, 270, 185-195; J. Catal., 2010, 274, 150-162; WO2010/048300 A1).